The present invention relates to an airbag and an airbag system for protecting an occupant in emergency such as a car crash, and more particularly, it relates to an airbag and an airbag system suitable for driver's seat airbag mounted to a steering.
Most of driver's seat airbag systems have an airbag mounted to a retainer in a folded condition and covered with a cover member called a module cover.
When a car impact has been sensed by a sensor, an inflator is activated to deploy an airbag by a gas (inflation gas) generated from the inflator.
Japanese Unexamined Patent Application Publication No. 2-74440 (incorporated by reference) discloses a driver's seat airbag that is divided into two chambers, a central chamber and an outer peripheral chamber, by a partition panel, the central chamber being first inflated and the outer peripheral chamber being next inflated. The partition panel has a gas circulation hole. The partition panel connects the rear and the front of the airbag and has the function of preventing the forward projection of the airbag during inflation. A vent hole is provided at the central chamber.
When the airbag disclosed in Japanese Unexamined Patent Application Publication No. 2-74440 (incorporated by reference) is inflated and an occupant strikes against an occupant, gas in the outer peripheral chamber easily flows out through the vent hole of the central chamber. Therefore, in order to maintain the gas pressure in the outer peripheral chamber high over a long time, an inflator with long duration of gas generation must be used. Employing the inflator, however, makes it difficult to control the inner pressure of the airbag.
Accordingly, it is an object of the present invention to provide an airbag and an airbag system capable of maintaining high inner pressure for a long time even with a low-capacity inflator as compared with the conventional one.
The present invention relates to an airbag provided on a high-speed mobile body such as a vehicle, which deploys in case of emergency such as a collision for protecting a human body.
Various airbag systems such as an airbag system for a driver's seat are used for protecting an occupant in case of emergency such as a collision or the like of a vehicle. The airbag system for a driver's seat includes an airbag formed by seaming peripheries of a front panel on the occupant side and of a rear panel on the opposite side. The rear panel is formed with an inflator engaging opening for receiving the extremity of the inflator at the center thereof. The circumference of the opening is attached to a retainer by a bolt, a pin, a rivet, and the like. The rear panel is formed with a vent hole for releasing gas in the airbag when the occupant of the driver's seat crushes into the airbag for absorbing an impact.
In order to protect a passenger in an emergency such as a car collision, a variety of airbag apparatuses including a driver-side airbag apparatus have been used. The driver-side airbag apparatus has an airbag formed by stitching together the circumferential portions of a front panel close to a passenger and a rear panel remote from the passenger. The rear panel has an opening for engagement with an inflator, formed at the central part thereof in order to accept the front of the inflator therein. The periphery of the opening is fixed to a retainer with bolts, pins, rivets, or the like. The rear panel has vent holes for releasing air in the airbag so as to absorb a shock when the passenger sitting in the driver's seat runs into the airbag.
In Japanese Unexamined Patent Application Publication No. 1-247242 (incorporated by reference), an airbag including an inner panel extending between an inflator insertion aperture on the rear panel and the front panel, and being divided in the interior thereof into a first chamber at the center and a second chamber circumferentially thereof is disclosed. The inner panel is substantially circular shape and the outer periphery thereof is connected to the midsection between the center and the periphery of the front panel. The inner panel is formed with the opening for the inflator at the center thereof, and the edge of the opening is attached to the retainer together with the rear panel. The inner panel is formed with a communication port for communicating the first chamber and the second chamber. When the inflator is actuated, the first chamber is deployed first, and the second chamber is deployed subsequently.
In the airbag in the same patent publication, since gas is flown into the second chamber from the first chamber through the communication port, completion of deployment of the second chamber is later than completion of deployment of the first chamber. In addition, it is difficult to adjust the internal pressure or the speed of deployment of the first chamber and the second chamber individually.
Japanese Unexamined Patent Application Publication No. 1-247242 (incorporated by reference) has disclosed an airbag in which an inner panel is disposed like extending between the inflator-engaging opening of the rear panel and the front panel so as to partition the inner space of the airbag into a first compartment and a second compartment. The inner panel has an approximately round shape when folded, and its outer circumferential portion is connected to an intermediate portion lying between the central portion and the circumferential portion of the front panel. The inner panel has an inflator-engaging opening at the central part thereof and the periphery of the opening is fixed to the retainer together with the rear panel. The inner panel has communication ports for mutual communication of the first compartment and the second compartment. When the inflator is activated, the first compartment inflates first and the second compartment inflates subsequently. Since gas flows into the second compartment from the first compartment through the communication ports, complete inflation of the second compartment lags behind complete inflation of the first compartment.